Japanese Laid-open Patent Publication No. 2006-54947 discloses a converter which performs regeneration to a power supply when a voltage across a DC link exceeds a predetermined upper limit voltage.
However, according to Japanese Laid-open Patent Publication No. 2006-54947, powering electric power and regenerative electric power are generated via the same A/C converter circuit, and thus the regenerative electric power generated at the time of decelerating the motor can not regenerated effectively.